Frame grid



March 19, 1963 A. L. CROSBY ETYAL 3,081,800

FRAME GRID 7 Filed March 31, 1959 3 Sheets-Sheet l 29 Im/I/Hlh 25/ INVENTORS ,4/fa/z L. Crosby BY Dar/d Aflander March 19, 1963 A. L. CROSBY ETAI. 3,081,800

FRAME GRID Filed March 31, 1959 3 Sheets-Sheet 2 INVENTORS A/fm L, Crosby BY Dar/d .4. Dander March 19, 1963 A. L. CROSBY ETAL FRAME GRID 3 Sheets-Sheet 3 Filed March 51, 1959 SM; w R Y Rm N 0 u R CV24 /m mmw A m W B United States Patent 3,081,890 FRAME GRID Alton L. Croshy, Austin, and David Andrew Dander, Emporium, Pin, assignors to Syivania Electric Products Inc, a corporation of Delaware Filed Mar. 31, 195?, Ser. No. 8%,317 3 Claims. (Cl. 14tl--71.5)

This invention relates generally to electron discharge devices and more specifically to grid structures for use in electron discharge devices.

The operating characteristics of space discharge de vices or electron tubes are related to and controlled in part by the form of the internal electrode structures and the accuracy or precision with which such structures are fabricated. For example, tube transconductance and signal to noise ratio are closely related to the selected size and spacing of lateral grid wires not only with respect to each other but also with respect to the position of other electrodes in the complete assembly.

As to the form of the supporting structure, ponventional mica-supported side rod type grid electrodes with laterals of sufficient strength at least to be partially self-supporting are satisfactory for many tube types. However, in electron tubes destined for operation in higher frequency ranges it may be necessary to provide grid structures having a high number of closely spaced and extremely fine lateral wires of a material too weak for attachment to conventional mica-supported side rods.

To overcome these problems the prior art teaches the use of a self-supporting grid frame upon which fine lateral grid wires are closely wound and attached to the sides of the frame by high temperature bonding techniques such as welding or brazing, or by the use of a fusible material such as glass frit.

From an electrical viewpoint grid electrodes made in accordance with the prior art appear to function satisfactorily; however, to date, the desired electrical characteristics have been purchased at a high cost resulting from lack of automatic fabrication techniques.

Thus it is an object of this invention to facilitate automatic production of frame type grid electrodes having a relatively large number of laterals per unit length of grid window.

It is a further object of this invention to provide an improved method of fabricating frame type grid electrodes made from high melting point metals such as molybdenum and tungsten.

It is also an object of this invention to simplify the process of attaching grid laterals to the supporting frame when the grid laterals are first placed on the frame.

It is still another object of this invention to minimize the need for high temperature type bonding techniques in the asembly of frame type grid electrodes.

Briefly, in one aspect of the invention there is provided an improved process for attaching lateral grid wire to a self-supporting frame of the type having two side rods held in fixed spaced relationship by upper and lower cross straps wherein a starting notch is placed in a side rod at one end of the frame, and a terminating notch is placed in a side rod at the other end of the frame. The grid winding is started by placing the starting portion of the grid wire in a starting notch which is closed thereafter to mechanically hold the grid wire. The grid is completed by winding a continuous length of grid wire through a plurality of turns equal to the number of grid laterals desired between the starting notch and the terminating notch and then closing the external wall of the terminating notch on the final end of the grid wire.

For a better understanding of the invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings, in which:

FIG. 1 shows the end view of a grid electrode strap type frame; and

PEG. 2 shows, in part, a side view of the frame of FIG. 1; and

FIG. 3 shows a portion of the stucture used to wind the grid; and

FIGS. 4 through 6 show the side rod notching position; and

FIGS. 7 and 8 show portions of a completed strap frame grid.

Referring to FIG. 1, there is shown the end view of a strap frame type grid supporting structure including side support elements or side rods 11 held inspaced relationship by upper cross straps 12.. As can be seen in the side view shown in FIG. 2, the complete frame structure also includes lower cross straps 13. Though other means for attaching the cross straps may be suitable in some embodiments it has been found that the cross straps may be welded to the side rods with satisfactory results, especially when the frame material is made from a high melting point material such as molybdenum. It is to be noted that, regardless of the material selected, the side rods should have a relatively smooth exterior surface, and the weld point between the cross straps and side rods should be reasonably free from flashing.

In FIG. 3 there is shown, in representative form, a portion of a winding machine including two rotating heads 15 and 19, both or either of which may be driven. Head 15 and a supporting mandrel tongue 17 are mounted for movement between a loading position, shown in dotted lines, and the Winding position shown in full lines. When head 15 and mandrel 17 are in the winding position both the tip of the mandrel tongue 17 and one end of the grid frame mounted thereon are received in a holding notch 18 in head 19. Head 15 is also notched to receive the other end of the mounted grid frame. The mandrel tongue 17 is of a length and cross section suitable for insertion with minimum clearance in the end opening of the strap frame as shown in FIG. 1, said end opening being defined by the internal surfaces of the side rods 11 and the internal surfaces of cross straps 12 and 13.

Lateral grid wire 2% is supplied from a spool or other supply means 21 which may include a tensioning device, not shown, such as a hysteresis motor or other device suitable for providing the wire tension desired during the winding step.

Assuming that the winding is to be made from left to right on the machine shown in FIG. 3, control over the pitch or turns per inch of the winding may be provided by a moving wire guide means such as jaws 22 and 23 attached to slide arm 25. Slide arm 25 is mounted for sliding movement from left to right on a support structure, not shown, through the action of attached cam roller 27, compression spring 29, and the cam surface of cam 31. Compression spring 29 is mounted, by means not shown, to force roller 27 against the surface of cam 31. Thus rotation of cam 31 in synchronous relationship with rotation of heads 15 and 19, from a power source not shown, makes it possible to feed lateral grid wire 20 through jaws 22 and 23 so as to provide any desired pitch of the grid laterals. As will be understood by those skilled in the art, cam 31 may be shaped to provide either a uniform or non-uniform pitch.

The bearings and drive means for heads 15 and 19 and for cam 31 as well as the necessary support structures for these elements and for slide arm 25 and wire supply 21 have been omitted from *FIG. 3 in the interest of clarity. Conventional structures for performing the necessary functions of support and drive will occur to those skilled in the art, and they form no part of the invention claimed herein.

At the start of the winding process head 15 and mandrel tongue 17 are in a position shown in dotted lines in FTG. 3. When in this position a strap frame is slid into place over the mandrel tongue 17, and then head 15 and loaded mandrel tongue 17 are moved into position for support and drive by head 19, i.e., the position shown in full lines in FIG. 3.

The first step before starting rotation of heads 15 and 19 is to form a transverse starting notch and a transverse terminating notch in a side rod 11 of the mounted strap frame somewhat as shown in FIG. 4. Though the starting notch and terminating notch have been shown in FIG. 4 and the remainder of the drawings to be formed in the same frame side rod 11, it is to be understood that the starting notch may be in one side rod and the terminating notch may be in the other side rod.

The preferred forms of starting and terminating notches are shown in FIGS. 4, and 6 where it can be seen that the internal wall 33 of the starting notch 35 slopes toward the internal wall 37 of the terminating notch 39. The differences between the notches shown in FIGS. 4, 5, and 6 are in the slope of the external walls 41 and 43. For example, in FIG. 4 both the external wall 41 of starting notch 35 and the external wall 43 of the terminating notch 39 are substantially vertical. In FIGS. 5 and 6 the external wall 41 of the starting notch 35 is slightly inclined toward the external portion of the frame. The same is true of the external wall 43 of the terminating notches 39 in FIGS. 5 and 6. Though the shape of the starting notch 35 and terminating notch 39 in FIG. 4 is preferred, it has been found that adding a slight slope to the external walls as shown in FIGS. 5 and 6 reduces wear on the notching tools. Though the notching tools 45 and 47 are shown in representative form above the notches in FIGS. 4, 5 and 6, it is to be understood that the notching tools actually are an integral part of the machine of FIG. 3.

' Referring again to FIG. 3, after the notching tools 45 and 47 have formed a starting notch 35 and a terminating notch 39, lateral wire 20 is fed through guide jaws 22 and 23 into and through the starting notch to place the starting portion of the grid lateral wire into the starting notch. Then as shown in FIG. 8, a plowing tool 49, or a peening tool 51 as shown in FIG. 7, closes the starting notch to mechanically hold the starting portion of the lateral grid winding. Immediately thereafter power is applied to rotate cam 31 and heads and 19 through the desired number of turns to form a helix of lateral grid wire in accordance with the desired pitch. When the lateral grid wire passes through the terminating notch the winding machine is either stopped automatically or manually in a position to bring terminating notch 39 immediately beneath a plowing tool 53 as best shown in FIG. 7 and FIG. 8.

The shape and size of the plowing tool 53 is important. It must be shaped and positioned relative to the terminating notch so as to be able to move the external wall 43 of the terminating notch over against the final end of the lateral grid winding without damaging the penultimate turn of the winding. The tool used to close the terminating notch must clear the wound laterals. For this reason a wide peening tool such as shown at 51 above the starting notch 35 in FIG. 7 has not been found suitable for closing the terminating notch 39.

The process herein described has been found extremely suitable for use in fabricating grid structures using a high melting point frame material such as molybdenum and lateral grid wires of tungsten. In most applications it will be unnecessary to bond the grid laterals to the side rods with high temperature bonding techniques.

all

However, if desired, after the grid has been wound the grid laterals may be attached to the side rods by brazing, welding, or with glass frit or some other high temperature bonding technique. In other words, fabrication of a grid in accordance with the teaching herein merely eliminates the need for high temperature bonding in most grids and does not bar the use of such a bonding technique to attach the grid laterals to the side rods after winding. Even so where such bonding is believed to be necessary, it will be found that the mechanical notching and plowing of the starting notch and the plowing of the terminating notch will greatly facilitate final grid fabrication by stabilizing the position of the lateral grid wires relative to the side rods prior to use of the selected bonding technique.

The size'of the frame side rods is determined by the desired grid minor which establishes the cathode to G spacing. The size of the lateral wires is governed to a great extent by lateral spacing which in turn is governed by the tube characteristics desired.

While there has been shown and described what is at present considered the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined in the appended claims.

Having thus described our invention we claim:

1. In a process of winding lateral grid wire on a grid support frame of the type having two side r'ods held in fixed spaced relationship by spaced upper and lower cross straps, the steps comprising forming a side rod starting notch closely adjacent the upper cross strap and a side rod terminating notch closely adjacent the lower cross strap with sufiicient space between said notches to support the desired number of grid laterals, said terminating notch having an internal sidewall and an external sidewall, placing the starting portion of the grid wire in the starting notch and closing the starting notch sufliciently to hold the grid wire, winding a continuous length of grid wire through a plurality of turns between said notches around the side rods into and through the terminating notch and plowing the external side wall of the terminating notch toward the internal side wall of the terminating notch to hold the terminating portion of the grid wire, said plurality of turns being sufiicient to form the desired number of grid laterals.

2. In the process of winding lateral grid wire on a grid support frame of the type having two side rods held in fixed spaced relationship by spaced upper and lower cross straps, the steps comprising simultaneously forming a transverse starting notch closely adjacent the upper cross strap and a transverse terminating notch closely adjacent the lower cross strap on a given side rod, with sufiicient space between said notches to support the desired number of grid laterals, said starting notch and said terminating notch each having an internal sidewall and an external sidewall, placing the starting portion of the grid wire in the starting notch and plowing the external wall of the starting notch toward the internal wall of the starting notch to fixedly 'hold the grid wire, winding a continuous length of grid wire through a plurality of turns, between said notches around the side rods into and through the terminating notch and plowing the external side wall of the terminating notch toward the internal side wall of the terminating notch to fixedly hold the remaining end of the grid wire, said plurality of turns being sufiicient to form the desired number of grid laterals.

3. .In a process of winding lateral grid wire on a grid support frame of the type having two side rods held in fixed spaced relationship by spaced upper and lower cross straps, the steps comprising simultaneously forming a transverse starting notch closely adjacent the upper cross strap and a transverse terminating notch closely adjacent the lower cross strap on a given side rod with sufiicient space between said notches to support the desired number of grid laterals, said terminating notch having an internal References Cited in the file of this patent sidewall and an external sidewall, placing the starting UNITED STATES PATENTS portion of the grid wire in the starting notch and closing the starting notch sufiiciently to hold the grid wire, wind- 1 5 "f g ing a continuous length of grid wire through a plurality 5 2181288 1939 of turns between said notches around the side rods into 2183635 B um 1939 and through the terminating notch and plowing the exat er ternal side wall of the terminating notch toward the in- 2225853 Baker et 1940 2,654,401 Legendre et al Oct. 6, 1953 ternal side wall of the terminating notch to fixedly hold the remaining end of the grid wire, said plurality of turns 10 being sufiicient to form the desired number of grid laterals.

2,759,499 Gartner Aug. 21, 1956 

1. IN A PROCESS OF WINDING LATERAL GRID WIRE ON A GRID SUPPORT FRAME OF THE TYPE HAVING TWO SIDE RODS HELD IN FIXED SPACED RELATIONSHIP BY SPACED UPPER AND LOWER CROSS STRAPS, THE STEPS COMPRISING FORMING A SIDE ROD STARTING NOTCH CLOSELY ADJACENT THE UPPER CROSS STRAP AND A SIDE ROD TERMINATING NOTCH CLOSELY ADJACENT THE LOWER CROSS STRAP WITH SUFFICIENT SPACE BETWEEN SAID NOTCHES TO SUPPORT THE DESIRED NUMBER OF GRID LATERALS, SAID TERMINATING NOTCH HAVING AN INTERNAL SIDEWALL AND AN EXTERNAL SIDEWALL, PLACING THE STARTING PORTION OF THE GRID WIRE IN THE STARTING NOTCH AND CLOSING THE STARTING NOTCH SUFFICIENTLY TO HOLD THE GRID WIRE, WINDING A CONTINUOUS LENGTH OF GRID WIRE THROUGH A PLURALITY OF TURNS BETWEEN SAID NOTCHES AROUND THE SIDE RODS INTO AND THROUGH THE TERMINATING NOTCH AND PLOWING THE EXTERNAL SIDE WALL OF THE TERMINATING NOTCH TOWARD THE INTERNAL SIDE WALL OF THE TERMINATING NOTCH TO HOLD THE TERMINATING PORTION OF THE GRID WIRE, SAID PLURALITY OF TURNS BEING SUFFICIENT TO FORM THE DESIRED NUMBER OF GRID LATERALS. 